Itching is a sign, not a diagnosis or specific disease. The most common causes of itching are parasites, infections, and allergies. There are many skin diseases that do not initially cause itching; however, itching may develop because of secondary bacterial or yeast infections. It is possible that by the time itching develops the initial cause is long gone.
Itching may be general or confined to one area. A horse with itchy skin will rub up against fences, stalls, trees, or other objects in an attempt to scratch the itch. The animal may excessively bite or lick its skin to the point of drawing blood or causing damage to the skin.
Your veterinarian will perform a thorough skin history and physical examination. Parasites are a common cause of itchy skin disorders in horses and are the first possible causes the veterinarian will seek to exclude. Infections are also common causes of itching and may be accompanied by hair loss, scaling, odor, and fluid discharge. Many infections can be effectively treated with appropriate antibiotics.
The underlying cause of itching may be allergic. The most common causes of allergic itching are insect bites, food allergy, and skin allergies. Sensitivity to insect bites is readily identified. Animals that have seasonal itching are likely reacting to seasonal allergens. Allergens in the feed are another possibility.
Successful treatment depends on identifying the underlying cause. For example, if parasites are identified as the cause of itching, appropriate antiparasitic drugs are prescribed. Horses with itching of unknown cause, or those in which treatment of the underlying disease does not eliminate the itching, will require medical management. Commonly prescribed anti-itching medications include corticosteroids and essential fatty acids.
A program that stresses preventive control of parasites in the horse’s environment—including insect control and regular deworming programs—can help eliminate or reduce some causes of itching.